BaM ferrite is a ferrimagnetic ceramic usually applied in high density recording media and as permanent magnet. This magnetic material shows high chemical stability, corrosion resistance and low production cost. This work shows the effects of barium excess on the BaM ferrite processing and on their magnetic properties. The use of barium excess had been used in some of ferrite industries to avoid the hematite and magnetite phase on the final products. In this work, barium ferrites were produced by traditional ceramic route and by combustion reaction (SHS) using barium nitrate and also barium carbonate. Two relations between barium and iron were used in all BaM ferrite processing, one stoichiometric (n = Fe2O3/BaO = 6) and another non-stoichiometric (n = Fe2O3/BaO = 5.45). All powders were submitted to different calcination conditions and analyzed by scanning electron microscopy, X-ray diffraction and magnetic characteristics. The presence of barium excess on the BaM ferrite resulted in the presence of the nonmagnetic BaFe2O4 phase that remains after the calcination and sintering processes. The BaFe2O4 phase is deleterious to the powder magnetic properties such as coercivity, remanence magnetic induction and BH Max. This damage was more significant on the BaM ferrite processed by SHS process, where the coercivity decreased in 28.8% and the BH Máx in 35,1%.The barium ferrite powder produced by traditional ceramic route shows high values of coercivity (4.28 kOe) and BH Max (0.87 MOe*emu/g), and the effect on the magnetic properties of barium excess was not so harmful than it was in the ferrite powders produced by SHS.
hexaferrites; traditional ceramic processes; combustion reaction
